• Journal of Korean Physical Therapy Science
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• v.9 no.1
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• pp.81-88
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• 2002

This paper presents a design and a control of a New Reciprocating Gait Orthosis and dynamic walking simulation for this system. The New Reciprocating Gait Orthosis is distinguished from other one by which has a very light-weight and a new RGO type with servo motors. The gait of a New Reciprocating Gait Orthosis depends on the constrains of mechanical kinematics and initial posture. The stability of dynamic walking is investigated by ZMP(Zero Moment Point) of the New Reciprocating Gait Orthosis. It is designed according to a human wear type and is able to accomodate itself to human environments. The joints of each leg are adopted with a good kinematic characteristics. To test of the analysis of joint kinematic properties, we did the strain stress analysis of dynamic PLS and the study of FEM with a dynamic PLS. It will be expect that the spinal card injury patients are able to train effectively with a Reciprocating Gait Orthosis. The New Reciprocating Gait Orthosis was able to keep smooth walling by the orthotic servo motors and hybrid system, make a sequence of flexion and extension of the joint during the walking. Also, the New Reciprocating Gait Orthosis turned out to be a satisfactory orthosis for walling training, for the spinal cord injury patient.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.3
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• pp.383-394
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• 2013

A sedimentation basin is used to remove suspended sediments which can cause abrasive and erosive wear on hydraulic turbines of hydropower plants. This sediment erosion not only decreases efficiency of the turbine but also increases maintenance costs. In this study, the three-dimensional numerical simulations were carried out on the overseas hydropower project. The simulations of flow and suspended sediment concentration were obtained using FLOW-3D computational fluid dynamics code. The simulations provide removal efficiency of a sedimentation basin based on particle sizes. The influence of baffles on the flow field and the removal efficiency of suspended sediments in the sedimentation basin has been investigated. This paper also provides the numerical simulations for sediment-induced density currents that may occur in the sedimentation basin. The simulation results indicate that the formation of density currents decreases the removal efficiency. When a baffle is installed in the sedimentation basin, the baffle provides intensive settling zones resulting in increasing the sediments settling. Thus the enhanced removal efficiency can be achieved by installing the baffle inside the sedimentation basin.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.882-887
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• 2003

This paper presented a design and control of a new RGO(reciprocating gait orthosis)and its simulation. The new RGO was distinguished from the other one by which had a very light-weight and a new RGO(reciprocating gait orthosis) system. The vibration evaluation of the hip joint system on the new RGO(reciprocating gait orthosis)was used to access by the 3-axis accelerometer with a low frequency vibration of less than 30 ㎐. The gait of the new RGO depended on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by analyzing the ZMP (zero moment point) of the new RGO. It was designed according to the human wear type and was able to accomodate itself to the environments of S.C.I. Patients. The joints of each leg were adopted with a good kinematic characteristics. To analyse joint kinematic properties, we made the hip joint system of FEM and the hip joint system by 1-axis and 3-axis Accelerometers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.507-513
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• 1998

In surface grinding, the conditions of the grinding wheel has much more significant effect on the machined workpiece as compared to other metal removal processes. The contact between the grinding wheel and the workpiece introduce heat and resistance, which restrict the self-dressing of the grits and result in burrs cracks on the workpiece. Therefore, before or during the grinding operation, it is necessary to self-dressing the grinding wheel for more accurate performance. In general, however, the choice of the dressing time has made by the operator's own decision or the condition of the workpiece. In this paper, a new method for finding the optimal dressing time of the grinding wheel is proposed. In order to develop a more sophisticated methodology, a non-contacting in-process optical measurement method using a laser beam has been introduced to find the glazing, loading, and spilling of the grinding wheel Simultaneously, a three-dimensional computer simulation of the grinding operation has been attempted based on the contact mechanism between the grinding wheel and the workpiece. The grains of the grinding wheel are simulated and the optimal dressing time is determined based on the amount of grain wear and work surface roughness.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.44-47
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• 2002

DV(Discrete Variation)-X${\alpha}$ cluster calculation was employed to calculate the electronic states of ${\gamma}'- Fe_4N$ which was one of iron nitride phases synthesized from plasma ion nitriding to improve surface hardness and wear resistance. The result of calculated electron density of states for Fe was similar to the result of band calculation. The cluster used for calculation of electronic states of ${\gamma}'-Fe_4N$ was based on $Fe_{14}N$ cluster which comprises 15 atoms. Finally the electronic states of ${\gamma}'- Fe_4N$ such as net-charge, band order, energy level, electron wave-function, and contour map for electron density were derived by the calculation.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.225-230
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• 2009

From the view point of railway vehicle dynamics, the interaction between wheel and rail have an huge effect on the behavior of the vehicle. This phenomenon is an unique motion, only for railway vehicles. Furthermore, close investigation of the backgrounds of the interaction is the key to estimate the dynamic behavior of the vehicle, successfully. To evaluate the model including flexible bodies such as car body and catenary system of the next generation express train, it is necessary to develop proper dynamic solver including a wheel rail contact module. In this study, wheel-rail contact module is developed using the general purpose dynamic solver. First of all, the procedure for calculation of the wheel-rail contact force has been established. Generally, yaw angle of the wheelset is ignored. Sets of information are summarized as tables and splined for further uses. With this information, normal force and creep coefficient can be extracted and used for FASTSIM algorithm, which has been shown good reliability over years. Normal force and longitudinal, lateral force at the contact surface are also calculated. Those data are verified by commercial railway simulation program 'VAMPIRE'. This procedure and program can offer a basic process for estimation of the dynamic behavior and wear of the wheel-rail system, even while running on the curved rail. Finally, multi-dimensional inspection tool will be developed including the prediction of the derailment.

• Tribology and Lubricants
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• v.36 no.6
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• pp.359-364
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• 2020

Numerical investigation of the groove trap effect with variation in the groove-edge radius of curvature is presented here. The trap effect is evaluated in a two-dimensional sliding bearing using computational fluid dynamics (CFD). This simulation is based on the discrete phase model (DPM) and standard k - ε turbulence model using commercial CFD software, FLUENT. The numerical results are evaluated by comparisons with streamlines and particle trajectories in the grooves. Grooves are applied to various lubrication systems to improve their lubrication characteristics, such as load carrying capacity increment, leakage reduction, frictional loss reduction, and preventing three-body abrasive wear due to trapping effect. This study investigates the grove trapping effect for various groove-edge radius of curvature values and Reynolds numbers. The particle is assumed to be made of steel, with a circular shape, and is injected as a single particle in various positions. One-way coupling is used in the DPM model because the single particle injection condition is applied. Further, the "reflect" condition is applied to the wall boundary and "escape" condition is used for the "pressure inlet" and "pressure outlet" boundaries. From the numerical results, the groove edge radius is found to influence the groove trap effect. Moreover, the groove trap effect is more effective when applying the groove edge radius.

• Fashion & Textile Research Journal
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• v.23 no.2
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• pp.237-246
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• 2021

This study aims to analyze short sleeve cycling tops from three brands for a change in garment fit and pressure depending on the static and cycling postures. To this end, it used a 3D virtual garment system to virtualize the garments. Further, a cross-section of the 3D virtual garment data was obtained, and the space length was measured in the design-X program to prove the objectivity of the 3D virtual garment. The results indicated that three brands had a large space length at the front than the back because of the bent posture in cycling. Therefore, appropriate ease was required for the waist and abdomen. Although there were various cutting lines of the bodice panel by brand, the design of the cutting lines should consider the changes in the surface to reflect the bent posture in cycling. The results of this experiment confirmed that the wrinkles present in the 3D virtual garment were reflected in the cross-section and that the space length was small in the high-stress area, as shown in red. Therefore, it was proven the stress of the 3D virtual garment could be used for 3D virtual garment evaluation.

• Journal of Fashion Business
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• v.27 no.6
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• pp.1-17
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• 2023

This study aimed to develop a modern textile design based on the formability of Frank Stella's paintings and to develop and present a fashion design that combines modern sensibility as a 3D virtual clothing program. The formative characteristics of Frank Stella's work were 'unity due to regular stripes', 'asymmetry due to geometric surface division', and 'decorabilitydue to colorful use'. Based on this, costume patterns and textiles based on Frank Stella's paintings were developed and six 3D virtual fashion design works were produced. The conclusion was as follows. First, it was confirmed that Frank Stella's work has a very wide range of applications to fashion products as abstract expression and minimal simplicity coexist visually. Second, various colors and forms of Frank Stella's paintings could be developed using textiles with visual formability, and originality as a fashion work applied with paintings could be maximized. Third, the development of 3D fashion using virtual programs had the ease of time efficiency, cost reduction, and spatiotemporal expansion of work processing compared to the actual costume production process. In addition, the simulation of 3D virtual wear made it easy to modify and recover the position of the textile to be applied to the costume and create a new design in the process of transforming the position of various textiles. It is expected that this study results will be used as basic data for the future conversion content industry in the painting and fashion industries.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.3940-3955
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• 2023

A new method of numerical simulating prediction and decontamination effect evaluation for abrasive jet decontamination to radioactively contaminated metal is proposed. Based on the Computational Fluid Dynamics and Discrete Element Model (CFD-DEM) coupled simulation model, the motion patterns and distribution of abrasives can be predicted, and the decontamination effect can be evaluated by image processing and recognition technology. The impact of three key parameters (impact distance, inlet pressure, abrasive mass flow rate) on the decontamination effect is revealed. Moreover, here are experiments of reliability verification to decontamination effect and numerical simulation methods that has been conducted. The results show that: ⁶⁰Co and other homogeneous solid solution radioactive pollutants can be removed by abrasive jet, and the average removal rate of Co exceeds 80%. It is reliable for the proposed numerical simulation and evaluation method because of the well goodness of fit between predicted value and actual values: The predicted values and actual values of the abrasive distribution diameter are Ф57 and Ф55; the total coverage rate is 26.42% and 23.50%; the average impact velocity is 81.73 m/s and 78.00 m/s. Further analysis shows that the impact distance has a significant impact on the distribution of abrasive particles on the target surface, the coverage rate of the core area increases at first, and then decreases with the increase of the impact distance of the nozzle, which reach a maximum of 14.44% at 300 mm. It is recommended to set the impact distance around 300 mm, because at this time the core area coverage of the abrasive is the largest and the impact velocity is stable at the highest speed of 81.94 m/s. The impact of the nozzle inlet pressure on the decontamination effect mainly affects the impact kinetic energy of the abrasive and has little impact on the distribution. The greater the inlet pressure, the greater the impact kinetic energy, and the stronger the decontamination ability of the abrasive. But in return, the energy consumption is higher, too. For the decontamination of radioactively contaminated metals, it is recommended to set the inlet pressure of the nozzle at around 0.6 MPa. Because most of the Co elements can be removed under this pressure. Increasing the mass and flow of abrasives appropriately can enhance the decontamination effectiveness. The total mass of abrasives per unit decontamination area is suggested to be 50 g because the core area coverage rate of the abrasive is relatively large under this condition; and the nozzle wear extent is acceptable.